This invention generally relates to apparatus for controlling the position of (a) video head(s) mounted on a rotary cylinder of video tape recorder, and more particularly, to such apparatus using a bimorph cell or element.
Amongst conventional video tape recorders, some of them are arranged such that a video head is fixed to a rotary cylinder for recording a video signal and for effecting normal playback, while another video head is additionally attached to a tip portion of a bimorph element which is fixed to the rotary head at the other end. This additional head is periodically moved in a direction normal to the plane of rotation thereof with a voltage being applied to the bimorph element so as to obtain accurate tracking on special playback, such as fast playback, slow playback, still playback, where the tape motion speed is different from that on recording.
However, since there is hysteresis in the relationship between the applied voltage and the displacement of the bimorph element, the amount of displacement cannot be simply determined by the applied voltage. Therefore, recording and normal playback cannot be effected by way of the video head attached to the bimorph element. As a result, conventional video tape recorders suffer from a drawback that four video heads in total, namely two for recording and the other two for special playback, are needed.